Wireless charging of an electronic device is a desirable convenience as the requirement to physically connect the device to a wire, dock or other physical component while charging is removed.
Some devices capable of near-field communications, referred to as near-field communication (NFC) tags or radio frequency identification (RFID) tags, can communicate with tag reader and can also be powered using energy extracted from signals received from the reader device. The tag has an antenna that is resonant at a frequency on which communications are transmitted from the reader in order to be able to receive as much energy as possible from the signal. This allows reliable communication as well as the extraction of power needed to operate the tag.
Some NFC or RFID capable devices may also include a battery so that they can operate when they are not being powered by a reader.